This invention relates to a wood working machine and more particularly, an automatic processing head replacement device for a complex processing NC (Numerical Control) type wood working machine which comprises a plurality of processing heads for performing different processing operations such as router-, drill-, grinding- and planing-heads each including a motor for operating each head independently of the other heads and in which any one of the heads selected for performing a selected processing operation is operated.
One example of the prior art automatic processing head replacement devices has been provided by the applicant of this application and shown in Japanese patent application publication No. 33281/1984. In the prior art processing head replacement device, a central column is provided with vertical rails on the front face thereof and a ram is mounted on the rails for slidable movement along the rails. The ram is moved upwardly and downwardly by a screw shaft which is rotated by a motor. Left- and right-hand horizontal beams are mounted on the left- and right-hand sides of the central column. The beams divert leftwards and rightwards, respectively, short of the ram to provide a predetermined clearance between the ram and the beams. Two horizontal rails are provided on each of the beams and the front face of the ram is also provided with upper and lower short rails which are adapted to connect between the rails on the left-and right-hand beams when the ram rails reach the same level as the beam rails.
A plurality of head holders (five head holders, for example) are vertically mounted in side by side relationship in a single row on the upper and lower rails, respectively, for leftward and rightward slidable movement along the respectively associated rails. When the rails on the left-and right-hand beams are connected to each other by the rails on the ram, the head holders can reciprocally move between the left- and right-hand beams and only one head holder is supported on the ram when the one head holder is positioned in the clearance defined between the ram and left- and right-hand beams and move upwardly in unison with the ram. A head base in mounted on the front face of each head holder to be adjusted in vertical position and as mentioned hereinabove, when the processing heads are attached to the head bases, the heads can be individually adjusted in vertical position. The ram can detachably hold only one processing head through one head holder at one time. The ram is provided with a connector which can provide power to only the one processing head held thereon. Only the one head held on the ram is moved in unison therewith and performs its assigned processing operation as the motor is driven. Horizontally supported on the left- and right-hand beams are left- and right-hand hydraulic cylinders which simultaneously slide leftwards and rightwards having five base holders pinched between the piston rods. Furthermore, in order to hold one processing head to be employed and now positioned in the clearance between the left- and right-hand beams, stopper electromagnets are provided on the left- and right-hand beams for regulating the slidable movement of the head holders by plungers and a plurality of such stopper electromagnets are fixedly secured to each beam in a predetermined spaced relationship. The ram also has similar stopper electromagnets fixedly secured thereto.
However, the prior art processing head replacement device having the components arranged and constructed as mentioned hereinabove has the following disadvantages:
(1) In optionally selecting one processing head out of a plurality of processing heads, two hydraulic cylinders and a plurality of stopper electromagnets are required and thus, the prior art processing head replacement device has a great number of parts and a complicate construction.
(2) In order to simultaneously sliding a plurality of head holders, the head holders are pinched between the piston rods of the left- and right-hand hydraulic cylinders, the hydraulic cylinders are alternately operated and the processing head positioning is effected by electrically turning the electromagnets on and off to regulate the slidable movement of the slide by the plungers of the cylinders. Thus, it is difficult to control oil pressure and precisely position the processing heads.
(3) Since a plurality of head holders are caused to abut against each other and moved with the holders pinched between the piston rods of the left- and right-hand hydraulic cylinders, when a processing head having the width larger than that of the head holders, spacers have to be interposed between the head holders so that the adjacent processing heads will not interfere with each other. And in connection with the interposing of the spacers, the position of the stopper electromagnets have to be varied accordingly.
(4) When the number of the head holders is varied, the design of the oil pressure control for the hydraulic cylinders have to changed accordingly.